JPS6172514A - Manufacture of foam insulator and its sizing die - Google Patents

Abstract

PURPOSE:To obtain the product with small eccentricity and excellent quality, regulating a sizing die in short time easily by achieving the position-regulation of the sizing die, while detecting the surface temperature of the foam insulating extrudate covering a core member by said sizing die provided with a temperature sensing element. CONSTITUTION:For instance, a core member and the high grade foam insulator 5 enclosing the core member are extruded from an extruding device 1 and are introduced into the cooled sizing die 2 with a cooling medium path 3. The distance between the sizing die 2 and the extruding device 1 and the position of the central axis of the sizing die 2 are regulated such that while detecting the surface temperature of said insulator 5 running in contact with the die at two positions or more in circumferential direction by the temperature sensing element 4 fitted to the rear portion 2' of said die, the difference therebetween is caused to become small and its value is caused to become correct. Thus, the objective product is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an improvement in a method for manufacturing foamed insulation and an apparatus thereof, and in particular to improved extrusion of low-foamed and high-foamed products in large-walled products. The present invention relates to a coating method and a sizing die with improved workability used therein.

[Conventional technology]

Conventionally, when covering a core material with a foamed insulator such as polyethylene, the extrusion coating is first carried out using an extrusion device, and at the same time as the foaming, the surface is molded using a sizing die to obtain a foamed insulator of excellent quality with a uniform surface. Manufacturing is underway.

[Problem that the invention seeks to solve]

However, the above sizing die has various technical problems. For example, if a foamed insulation is sized excessively, the frictional resistance when the surface of the foamed insulation is rubbed against the inner surface of the sizing die causes the bubbles in the foamed insulation to burst and connect with adjacent ones, creating what is commonly called a cavity. do. In order to solve this problem, a method of coating the inner surface of the sizing die with a material such as Teflon, which has a low coefficient of friction, was invented and has already been filed as Japanese Patent Application No. 32,971/1982. However, even if this method is used, there is a limit, and it is important to avoid excessive friction and to mold with appropriate friction.

Conventional sizing gouges are often made of metal cylinders with good heat conductivity because sizing must be done while cooling with a cooling medium, but since the inside of the sizing goug cannot be seen with the naked eye, the foamed insulator is molded by moderate friction. There is no way to know if there are any.

In general, in order to mold with moderate friction, it is important to select the inner diameter of the sizing die and determine the separation distance between the extrusion device and the sizing die.The latter is especially important when it comes to actually extruding the foamed insulator and checking its foaming state. The position is adjusted by visual observation to achieve the best sizing, but there is a considerable loss in preparation time and materials.

Furthermore, if the center axis of the sizing die does not align with the center axis of the foamed insulator, problems such as the surface of the foamed insulator not being smooth or the formation of cavities will occur. This is because the degree of sizing in the circumferential direction on the surface of the insulator is not uniform, and in order to eliminate this problem, K also spends a considerable amount of time and materials adjusting the center axis of the sizing die.

Particularly unique to high-foam insulation extrusion, the surface before entering the sizing die is usually highly uneven and uneven, making positioning of the sizing die extremely difficult.

In view of the current state of these sizing dies, the present invention aims to solve the above-mentioned technical problems and provide a manufacturing method and sizing die that can be adjusted with easy operation.

[Means for solving problems]

The present invention is a method for extruding a foamed insulator onto a core material. After the core material is extruded and coated with a foamed insulator, the surface temperature is measured using a sizing die equipped with a temperature sensing element that detects the surface temperature of the foamed insulator. A method for manufacturing a foamed insulator characterized by detecting and adjusting the position of a sizing die according to the displayed value, and a sizing die for sizing the foamed insulator, in which two or more temperature sensing elements are attached to the sizing die. The present invention relates to a sizing die characterized in that the above-mentioned objects are achieved.

That is, the manufacturing method and sizing die of the present invention are as follows:
Attach temperature sensing elements to detect the surface temperature of the foamed insulator at two or more places in the circumferential direction of the sizing die, and while measuring the surface temperature, make sure that there is no difference in temperature towards each temperature sensing element. This method is characterized by adjusting the inclination of the sizing die with a distance between the sizing die and the extrusion device 1"L so that the temperature value falls within the range of forging pressure. In other words, sizing with low gamma Since the surface temperature of the foamed insulator drops rapidly when it comes into contact with the die, the degree of sizing, especially the non-uniformity, is intended to be interpreted as the surface temperature of the highly foamed insulator, especially the temperature difference.

Examples of the temperature sensing element of the present invention include contact type thermometers, such as thermocouple type plate-shaped and needle thermometers, and non-contact type thermometers, such as radiation type thermometers, and the well-known thermometer Nepheize I7 type Onho Needle Ring. Which feeling? a
Any element can be used, as long as the temperature can be kept extremely low. Note that when measuring the surface temperature of a traveling soft foam, a non-contact type is preferable to a contact type.

This will be explained below using FIG. 1 as an example. FIG. 1 (Al is a side view for schematic explanation of one embodiment of the manufacturing method and sizing die of the present invention, (B) is a sectional view taken along the A-A' cross section,
is an extrusion device, and the core material is supplied by a feeder (not shown). 5 is a highly foamed insulator coated around the core material, and immediately after leaving the extrusion device, it usually begins to foam rapidly in an irregular shape and enters the sizing die 2. The sizing die usually has a cooling medium passage as indicated by 5 and is cooled.

While the highly foamed insulator is being sized with a sizing die 2, its temperature is measured with a temperature sensing element 4 attached to its rear part 2'. This temperature sensing element 4 is capable of detecting the surface temperature when the highly foamed insulator runs in contact with it, and a known means for measuring surface temperature is used.

Note that these temperature sensing elements are sometimes attached by carving the inner surface of the sizing die depending on the size of the temperature sensing element so as not to damage the surface of the highly foamed insulator and prevent the portion from becoming a convex portion.

Further, although the mineral temperature sensing element is attached to the rear part of the sizing die in FIG. 1, it is also possible to attach it to the middle part of the sizing die. Of course, it may not be completely integrated with the sizing die, but may be installed with an appropriate amount of PHf.

This temperature sensing element detects the extent to which the surface of the foamed insulator is cooled by the sizing die, that is, the extent to which it is in contact with the sizing die and is molded. It is necessary to install more than one, but two or four are sufficient in most cases.

These thermosensors detect the surface temperature of the foam insulator at two or more locations in the circumferential direction, and the sizing die and extrusion device are designed to minimize the difference between them and to maintain the appropriate value. Adjust the distance and the position of the center axis of the sizing die. Note that the above-mentioned appropriate temperature value may be determined in advance based on the surface condition of the sized foam insulator, the finished outer diameter, etc., and the displayed value at that time depending on the type of the temperature sensing element.

〔Example〕

Example 1 Using the configuration shown in FIG.
TH-BM type wire thermometers (non-contact) manufactured by Tokyo Seiko Co., Ltd. were attached to the tubes in four directions. A manual 71 noddle was attached to the sizing die so that it could be freely moved in any direction up and down, left and right, and front and back. Extrusion device 1 extrudes foamed polyethylene 5 at a temperature of 100°C, and sizing die 3
was cooled with 20°C water. The surface temperature of the foam was measured using the above-mentioned thermometer, and extrusion was performed while operating the noddle so that the difference in surface temperature of the foam was 5° C. or less.

As a result, a foamed polyethylene insulated wire was obtained in which the surface condition of the foam was uniform all the way around and the outer diameter area ratio was 10% or less.

The time required to operate the sizing die at this time was 1
It took less than 0 minutes, which was a huge time reduction compared to the conventional method (about 30 minutes). Furthermore, when repeated operations were performed, the reproducibility was much better than that of conventional methods.

〔Effect of the invention〕

The manufacturing method and sizing die of the present invention described above enable the position pA of the sizing die to be adjusted while observing the displayed value regarding the surface temperature from the temperature sensing element, so adjustment can be easily made in a very short time, and This has the great effect of making it possible to automatically control sizing, which was previously impossible.

This manufacturing method is extremely effective when a non-eccentric crosshead is used in the extruder and an insulator with extremely low eccentricity is extruded, since the good eccentricity is not diminished by sizing.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the fJI manufacturing method and sizing die according to the present invention, where the figure is a side view, (I31 is an A-A' sectional view, 2 and 2' are sizing dies, 3 is a cooling medium passage, and 4 is a sensing die. The temperature element is shown.

Claims (2)

[Claims] (1) In the method of extrusion manufacturing a foamed insulator on a core material, after the foamed insulator is extruded and coated on the core material, the surface of the foamed insulator is A method for producing a foamed insulator, characterized by detecting temperature and adjusting the position of a sizing die according to the displayed value. (2) A sizing die for sizing a foamed insulator, characterized in that two or more temperature sensing elements are attached to the sizing die.